Auto merge of #5824 - tmiasko:manually-drop-clone, r=Manishearth

Ignore not really redundant clones of ManuallyDrop

"Redundant" clones of `ManuallyDrop` are sometimes used for the side effect of
invoking the clone, without running the drop implementation of the inner type.
In other words, they aren't really redundant. For example, futures-rs crate:

```rust
#[allow(clippy::redundant_clone)] // The clone here isn't actually redundant.
unsafe fn increase_refcount<T: ArcWake>(data: *const ()) {
    // Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
    let arc = mem::ManuallyDrop::new(Arc::<T>::from_raw(data as *const T));
    // Now increase refcount, but don't drop new refcount either
    let _arc_clone: mem::ManuallyDrop<_> = arc.clone();
}
```

changelog: Ignore redundant clone lint for ManuallyDrop.

0 files changed, 0 insertions, 0 deletions